1. Field of the Invention
This invention relates to well tools and more particularly to apparatus and methods for testing wells, particularly existing wells, for obtaining information needed for reservoir analysis.
2. Description of the Prior Art
For many years downhole well data were generally obtained by lowering a bottom hole pressure gage into a well on a wire line after the well had been closed in for a period, say 48 to 72 hours, to permit the well bore pressure to equalize with that of the surrounding producing formation. A maximum recording thermometer was generally run with the gage. Pressure readings were often made at several locations, and especially at or near the formation. After obtaining such static readings, the well was then placed on production and pressure readings taken while the well was flowing. Thus, information was obtained on the drawdown and the build-up characteristics of the producing formation. In recent years, well testing and reservoir analysis have become more highly developed and efficient. The information gathered as a result of such well testing is subsequently evaluated by reservoir technicians to aid in their efforts to determine with greater accuracy the extent, shape, volume, and contents of the reservoir tested.
Formerly, flow tests were conducted while controlling the flow with valves located at the surface, but in recent years, many tests have been conducted using well tools which control the flow of the well at a location at or close to the formation. Thus the build-up and drawdown periods are shortened considerably and the information obtained is more accurate. Tools for such testing are generally run on an electric cable and include a valve which is landed in a receptable near the level of the formation and which may be opened and closed merely by tensioning and slacking the cable. Included in the tool string is generally a pressure sensor which senses the pressure below the valve at all times and sends suitable signals via the cable to the surface where the signal is processed by surface readout equipment for display and/or recording. Such signals are sent at intervals, say every few seconds, or every few minutes.
Known prior art U.S. patents are: U.S. Pat. Nos. Re 31,313, 2,673,614, 2,698,056, 2,920,704, 3,208,531, 4,051,897, 4,069,865, 4,134,452, 4,149,593, 4,159,643, 4,252,195, 4,274,485, 4,278,130, 4,286,661, 4,373,583, 4,417,470, 4,426,882, 4,487,261, 4,568,933, 4,583,592.
Also, Applicant is familiar with a brochure published by Flopetrol-Johnston covering their MUST Universal DST (Drill Stem Test) device.
In addition, they are familiar with the landing nipples and lock mandrels illustrated on page 5972 of the Composite Catalog of Oil Field Equipment and Services, 1980-81 Edition, published by WORLD OIL magazine. Those landing nipples and locking devices are based upon U.S. Pat. No. 3,208,531.
U.S. Pat. No. 4,051,897 issued to George F. Kingelin on Oct. 4, 1977; U.S. Pat. No. 4,069,865 issued Jan. 24, 1978 to Imre I. Gazda and Albert W. Carroll; U.S. Pat. No. 4,134,452 issued to George F. Kingelin on Jan. 16, 1979; U.S. Pat. No. 4,149,593 issued to Imre I. Gazda, et al, on Apr. 17, 1979; U.S. Pat. No. 4,159,643 issued to Fred E. Watkins on July 3, 1979; U.S. Pat. No. 4,286,661 issued on Sept. 1, 1981 to Imre I. Gazda; U.S. Pat. No. 4,487,261 issued to Imre I. Gazda on Dec. 11, 1984; U.S. Pat. No. 4,583,592 issued to Imre I. Gazda and Phillip S. Sizer on Apr. 22, 1986; and U.S. Pat. No. Re. 31,313 issued July 19, 1983 to John V. Fredd and Phillip S. Sizer, on reissue of their original U.S. Pat. No. 4,274,485 which issued on June 23, 1981, all disclose test tools which may be run on a wire line or cable and used to open and close a well at a downhole location by pulling up or slacking off on the wire line or cable by which test tools are lowered into the well. In some of the above cases, a receptacle device is first run on a wire line and anchored in a landing nipple, then a probe-like device is run subsequently and latched into the receptacle. In the other cases, the receptacle is run in as part of the well tubing.
U.S. Pat. Nos. 4,051,897; 4,069,865; and 4,134,452 provide only a tiny flow passage therethrough openable and closable by tensioning and relaxing the conductor cable for equalizing pressures across the tool.
U.S. Pat. No. 4,149,593 is an improvement over the device of U.S. Pat. No. 4,134,452 and provides a much greater flow capacity as well as a latching sub which retains the tool in the receptacle with a tenacity somewhat proportional to the differential pressure acting thereacross.
U.S. Pat. No. 4,286,661 is a division of U.S. Pat. No. 4,149,593, just discussed, and discloses an equalizing valve for equalizing pressures across the device disclosed in U.S. Pat. No. 4,149,593.
U.S. Pat. No. 4,159,643 discloses a device similar to those mentioned above and has a relatively small flow capacity. This tool has lateral inlet ports which are closed by tensioning the conductor cable.
U.S. Pat. No. 4,373,583 discloses a test tool similar to those just discussed. It carries a self-contained recording pressure gage suspended from its lower end and therefore sends no well data to the surface during the testing of a well. This tool, accordingly, may be run on a conventional wire line rather than a conductor line, since it requires no electrical energy for its operation.
The MUST Drill Stem Test Tool of Flopetrol-Johnston disclosed in the brochure mentioned above provides a nonretrievable valve opened and closed from the surface by tensioning and relaxing the conductor cable connected to the probe-like tool latched into the valve. Even with the valve open and the well producing, no flow takes place through the probe. All flow moves outward through the side of the valve into bypass passages which then empty back into the tubing at a location near but somewhat below the upper end of the probe. The device provides considerable flow capacity. The probe automatically releases when a predetermined number (up to twelve) of open-close cycles have been performed.
U.S. Pat. No. 2,673,614 issued to A. A. Miller on Mar. 30, 1954; U.S. Pat. No. 2,698,056 which issued to S. J. E. Marshall et al. on Dec. 28, 1954; U.S. Pat. No. 2,920,704 which issued to John V. Fredd on Jan. 12, 1960; and U.S. Pat. No. 3,208,531 issued to J. W. Tamplen on Sept. 28, 1965 disclose various well-known devices for locking well tools in a well flow conductor.
U.S. Pat. No. 2,673,614 shows keys having one abrupt shoulder engageable with a corresponding abrupt shoulder in a well for locating or stopping a locking device at the proper location in a landing receptacle for its locking dogs to be expanded into a lock recess in the receptacle. A selective system is disclosed wherein a series of similar but slightly different receptacles are placed in a tubing string. A locking device is then provided with a selected set of locator keys to cause the device to stop at a preselected receptacle.
U.S. Pat. No. 3,208,531 discloses a locking device which uses keys profiled similarly to the keys of U.S. Pat. No. 2,673,614 but performing both locating and locking functions.
U.S. Pat. No. 4,252,195 discloses use of a pressure probe run on an electric cable and engaged in a transducer fitting downhole. The well is opened and shut by a valve near the transducer fitting in response to the differential pressure between annulus pressure and tubing pressure while signals are transmitted to the surface by the pressure gage to indicate the pressures sensed thereby.
U.S. Pat. No. 4,278,130 discloses apparatus having a ball valve for opening and closing the well while a pressure probe engaged in a spider receptacle senses well pressure in either flow or shut-in state and sends appropriate signals to the surface indicating the pressures measured.
U.S. Pat. No. 4,426,882 discloses drill stem test apparatus which includes an electric pressure gage with surface readout. The downhole valve of the test apparatus is controlled electro-hydraulically to open and close the well at the test tool.
U.S. Pat. No. 4,568,933 discloses a test tool to be run into a well on a single electric cable. Sensors carried by the tool sense, for instance, fluid pressure, temperature, fluid flow and its direction, and the presence of pipe collars, and sends corresponding signals to the surface readout equipment for real-time display and/or recording. All such signals are transmitted via the single-conductor electric cable.
U.S. Pat. No. 4,417,470 discloses an electronic temperature sensor for use in a downhole well test instrument, the sensor having a very rapid response to changes in well fluid temperatures.
The present invention is an improvement over the inventions disclosed in U.S. Pat. Nos. 4,149,593; 4,159,643; 4,487,261; 4,583,592; and Re. 31,313 (originally 4,274,485), and these patents are incorporated into this application for all purposes by reference thereto.
Using known tools and methods such as disclosed in some of the patents discussed hereinabove, a well may be closed in at a location near the producing formation to allow the natural formation pressure to build beneath the well packer, or opening the well to flow to cause a drawdown of pressure, such build-up and drawdown pressures being monitored by the test tool and signals corresponding to the pressures measured sent to a surface readout to display and/or record the test information in real time for evaluation as desired.
There was not found in the prior art an invention disclosing test apparatus providing a test tool having a valve engageable in a landing receptacle and provision for monitoring the pressures both above and below the shut-in point and transmitting such test information to a surface readout for real-time display and/or recording.